Dose counters for inhalers, inhalers and methods of assembly thereof

ABSTRACT

An inhaler for inhaling medicament and having a body, the body have a main part thereof for retaining a medicament store; and a dose counter, the dose counter being located in a dose counter chamber of the body which is separated from the main part of the body, the dose counter chamber of the body having a dosage display and a perforation so as to permit the evaporation of water or aqueous matter in the dose counter chamber into the atmosphere.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional patent application of U.S.patent application Ser. No. 14/103,324, filed Dec. 11, 2013, which is adivisional application of U.S. patent application Ser. No. 13/110,532,filed May 18, 2011, which claims priority to U.S. Provisional PatentApplication No. 61/345,763, filed May 18, 2010, and U.S. ProvisionalPatent Application No. 61/417,659, filed Nov. 29, 2010, each of which isincorporated herein by reference in its entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates to dose counters for inhalers, inhalersand methods of assembly thereof. The invention is particularlyapplicable to metered dose inhalers including dry power medicamentinhalers, breath actuated inhalers and manually operated metered dosemedicament inhalers.

BACKGROUND OF THE INVENTION

Metered dose inhalers can comprise a medicament-containing pressurisedcanister containing a mixture of active drug and propellant. Suchcanisters are usually formed from a deep-dawn aluminium cup having acrimped lid which carries a metering valve assembly. The metering valveassembly is provided with a protruding valve stem which, in use isinserted as a push fit into a stem block in an actuator body of aninhaler having a drug delivery outlet. In order to actuate a manuallyoperable inhaler, the user applies by hand a compressive force to aclosed end of the canister and the internal components of the meteringvalve assembly are spring loaded so that a compressive force ofapproximately 15 to 30N is required to activate the device in sometypical circumstances.

In response to this compressive force the canister moves axially withrespect to the valve stem and the axial movement is sufficient toactuate the metering valve and cause a metered quantity of the drug andthe propellant to be expelled through the valve stem. This is thenreleased into a mouthpiece of the inhaler via a nozzle in the stemblock, such that a user inhaling through the outlet of the inhaler willreceive a dose of the drug.

A drawback of self-administration from an inhaler is that it isdifficult to determine how much active drug and/or propellant are leftin the inhaler, if any, especially of the active drug and this ispotentially hazardous for the user since dosing becomes unreliable andbackup devices not always available.

Inhalers incorporating dose counters have therefore become known.

WO 98/280733 discloses an inhaler having a ratchet mechanism for drivinga tape drive dose counter. A shaft onto which tape is wound has afriction clutch or spring for restraining the shaft against reverserotation.

EP-A-1486227 discloses an inhaler for dry powered medicament having aratchet mechanism for a tape dose counter which is operated when amouthpiece of the inhaler is closed. Due to the way in which themouthpiece is opened and closed, and actuation pawl of the device whichis mounted on a yoke, travels a known long stroke of consistent lengthas the mouthpiece is opened and closed.

WO 2008/119552 discloses a metered-dose inhaler which is suitable forbreath-operated applications and operates with a known and constantcanister stroke length of 3.04 mm+/−0.255 mm. A stock bobbin of thecounter, from which a tape is unwound, rotates on a shaft having a splitpin intended to hold the stock bobbin taut. However, some dose countersdo not keep a particularly reliable count, such as if they are droppedonto a hard surface.

More recently, it has become desirable to improve dose counters furtherand, in particular, it is felt that it would be useful to provideextremely accurate dose counters for manually-operated canister-typemetered dose inhalers. Unfortunately, in these inhalers, it has beenfound in the course of making the present invention that the strokelength of the canister is to a very large extent controlled on each doseoperation by the user, and by hand. Therefore, the stroke length ishighly variable and it is found to be extremely difficult to provide ahighly reliable dose counter for these applications. The dose countermust not count a dose when the canister has not fired since this mightwrongly indicate to the user that a dose has been applied and if donerepeatedly the user would throw away the canister or whole device beforeit is really time to change the device due to the active drug andpropellant reaching a set minimum. Additionally, the canister must notfire without the dose counter counting because the user may then applyanother dose thinking that the canister has not fired, and if this isdone repeatedly the active drug and/or propellant may run out while theuser thinks the device is still suitable for use according to thecounter. It has also been found to be fairly difficult to assembly someknown inhaler devices and the dose counters therefor. Additionally, itis felt desirable to improve upon inhalers by making them easily usableafter they have been washed with water.

The present invention aims to alleviate at least to a certain extent oneor more of the problems of the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided adose counter for an inhaler, the dose counter having a counter displayarranged to indicate dosage information, a drive system arranged to movethe counter display incrementally in a first direction from a firststation to a second station in response to actuation input, wherein aregulator is provided which is arranged to act upon the counter displayat the first station to regulate motion of the counter display at thefirst station to incremental movements.

The regulator is advantageous in that it helps prevent unwanted motionof the counter display if the counter is dropped.

According to a further aspect of the present invention, the regulatorprovides a resistance force of greater than 0.1 N against movement ofthe counter display. According to still a further aspect of the presentinvention, the resistance force is greater than 0.3 N. According to yeta further aspect of the present invention, the resistance force is from0.3 to 0.4 N.

Preferably, the counter comprises a tape.

Preferably, the tape has dose counter indicia displayed thereon. Thefirst station may comprise a region of the dose counter where tape isheld which is located before a display location, such as a displaywindow, for the counter indicia.

The first station may comprise a first shaft, the tape being arranged onthe first shaft and to unwind therefrom upon movement of the counterdisplay.

The first shaft may be mounted for rotation relative to a substantiallyrotationally fixed element of the dose counter.

The regulator may comprise at least one projection which is arranged onone of the first shaft and the substantially rotationally fixed elementand to engage incrementally with one or more formations on the other ofthe first shaft and the substantially rotationally fixed element.

At least two said projections may be provided. Exactly two saidprojections maybe provided.

Each projection may comprise a radiused surface.

The at least one projection may be located on the substantially fixedelement which may comprise a fixed shaft which is fixed to a main bodyof the dose counter, the first shaft being rotationally mounted to thefixed shaft.

Preferably, the fixed shaft has at least two resiliently flexible legs(or forks). Each leg may have at least one said projection formed in anoutwardly facing direction thereon, said one or more formations beingformed on an inwardly facing engagement surface of the first shaft, saidat least one projection being arranged to resiliently engage said one ormore formations. Preferably, a series of said formations are provided.An even number of said formations may be provided. Eight to twelve ofsaid formations may be provided. In one embodiment, ten said formationsare provided.

Each said formation may comprise a concavity formed on an engagementsurface. Each concavity may comprise a radiused surface wall portionwhich preferably merges on at least one side thereof into a flat wallportion surface. The engagement surface may include a series of saidconcavities, and convex wall portions of the engagement surface may beformed between each adjacent two said concavities, each said convex wallportion comprising a convex radiused wall portion.

Each convex radiused wall portion of each convex wall portion may beconnected by said flat wall portion surfaces to each adjacent concavity.

The fixed shaft may comprise a split pin with fork legs and eachprojection may be located on a said fork leg.

The first shaft may comprise a substantially hollow bobbin.

Said at least one formation may be located on an inner surface of thebobbin. In other embodiments it may be located on an outer surfacethereof. Said engagement surface may extend partially along said bobbin,a remainder of the respective inner or outer surface having a generallysmooth journal portion along at least a portion thereof.

The drive system may comprise a tooth ratchet wheel arranged to act upona second shaft which is located at the second station, the second shaftbeing rotatable to wind the tape onto the second shaft.

The second shaft may be located on a main body of the dose counterspaced from and parallel to the first shaft.

The ratchet wheel may be fixed to the second shaft is arranged to rotatetherewith. The ratchet wheel may be secured to an end of the secondshaft and aligned coaxially with the second shaft.

The dose counter may include anti-back drive system which is arranged torestrict motion of the second shaft. The anti-back drive system mayinclude a substantially fixed tooth arranged to act upon teeth of theratchet wheel.

According to a further aspect of the present invention, a dose counterincludes an anti-back drive system which is arranged to restrict motionof the second shaft in a tape winding direction.

According to a further aspect of the present invention there is provideda shaft for holding counter tape in a dose counter for an inhaler, theshaft having an engagement surface including incrementally spacedformations located around a periphery thereof, the formations comprisinga series of curved concavities and convex portions.

The shaft may comprise a hollow bobbin.

The engagement surface may be a generally cylindrical inwardly directedsurface.

The engagement surface may include a flat surface wall portion joiningeach concavity and convex wall portion.

Each concavity may comprise a radiused wall portion.

Each convex wall portion may comprise a radiused wall portion.

Said concavities may be regularly spaced around a longitudinal axis ofthe shaft.

Said convex wall portions may be regularly spaced around a longitudinalaxis of the shaft.

In some embodiments there may be from eight to twelve said concavitiesand/or concavities regularly spaced around a longitudinal axis thereof.

One embodiment includes ten said concavities and/or convex wall portionsregularly spaced around a longitudinal axis of the shaft.

According to a further aspect of the present invention there is provideda shaft and counter tape assembly for use in a dose counter for aninhaler, the assembly comprising a rotatable shaft and a counter tapewhich is wound around the shaft and is adapted to unwind therefrom uponinhaler actuation, the shaft having an engagement surface which includesincrementally spaced formations located around a periphery thereof.

According to a further aspect of the present invention there is providedan inhaler for the inhalation of medication and the like, the inhalerincluding a dose counter as in the first aspect of the presentinvention.

A preferred construction consists of a manually operated metered doseinhaler including a dose counter chamber including a dose display tapedriven by a ratchet wheel which is driven in turn by an actuator pawlactuated by movement of a canister, the tape unwinding from a stockbobbin during use of the inhaler, a rotation regulator being providedfor the stock bobbin and comprising a wavelike engagement surface withconcavities which engage against control elements in the form ofprotrusions on resilient forks of a split pin thereby permittingincremental unwinding of the stock bobbin yet resisting excessiverotation if the inhaler is dropped onto a hard surface.

According to another aspect of the present invention there is provided adose counter for a metered dose inhaler having a body arranged to retaina medicament canister of predetermined configuration for movement of thecanister relative thereto; the dose counter comprising: an incrementalcounting system for counting doses, the incremental counting systemhaving a main body, an actuator arranged to be driven in response tocanister motion and to drive an incremental output member in response tocanister motion, the actuator and incremental output member beingconfigured to have predetermined canister fire and count configurationsin a canister fire sequence, the canister fire configuration beingdetermined by a position of the actuator relative to a datum at whichthe canister fires medicament and the count configuration beingdetermined by a position of the actuator relative to the datum at whichthe incremental count system makes an incremental count, wherein theactuator is arranged to reach a position thereof in the countconfiguration at or after a position thereof in the canister fireconfiguration.

This arrangement has been found to be highly advantageous since itprovides an extremely accurate dose counter which is suitable for usewith manually operated metered dose inhalers. It has been found thatdose counters with these features have a failure rate of less than 50failed counts per million full canister activation depressions. It hasbeen found in the course of making the present invention that highlyreliable counting can be achieved with the dose counter counting at orsoon after the point at which the canister fires. It has been is coveredby the present inventors that momentum and motion involved in firing thecanister, and in some embodiments a slight reduction in canister backpressure on the user at the time of canister firing, can very reliablyresult in additional further motion past the count point.

The actuator and incremental counting system may be arranged such thatthe actuator is displaced less than 1 mm, typically 0.25 to 0.75 mm,more preferably about 0.4 to 0.6 mm, relative to the body between itslocation in the count and fire configurations, about 0.48 mm beingpreferred. The canister, which can move substantially in line with theactuator, can reliably move this additional distance so as to achievevery reliable counting.

The incremental count system may comprise a ratchet mechanism and theincremental output member may comprise a ratchet wheel having aplurality of circumferentially spaced teeth arranged to engage theactuator.

The actuator may comprise an actuator pawl arranged to engage on teethof the ratchet wheel. The actuator pawl may be arranged to be connectedto or integral with an actuator pin arranged to engage and be depressedby a medicament canister bottom flange. The actuator pawl may begenerally U-shaped having two parallel arms arranged to pull on acentral pawl member arranged substantially perpendicular thereto. Thisprovides a very reliable actuator pawl which can reliably pull on theteeth of the ratchet wheel.

The incremental count system may include a tape counter having tape withincremental dose indicia located thereon, the tape being positioned on atape stock bobbin and being arranged to unwind therefrom.

The actuator and incremental output member may be arranged to provide astart configuration at which the actuator is spaced from the ratchetoutput member, a reset configuration at which the actuator is broughtinto engagement with the incremental output member during a canisterfire sequence, and an end configuration at which the actuator disengagesfrom the ratchet output during a canister fire sequence.

The actuator may be arranged to be located about 1.5 to 2.0 mm, from itslocation in the fire configuration, when in the start configuration,about 1.80 mm being preferred.

The actuator may be arranged to be located about 1.0 to 1.2 mm, from itslocation in the fire configuration, when in the reset configuration,about 1.11 mm being preferred.

The actuator may be arranged to be located about 1.1 to 1.3 mm, from itslocation in the fire configuration, when in the end configuration, about1.18 mm being preferred.

These arrangements provide extremely reliable dose counting, especiallywith manually operated canister type metered dose inhalers.

The main body may include a formation for forcing the actuator todisengage from the incremental output member when the actuator is movedpast the end configuration. The formation may comprise a bumped upportion of an otherwise generally straight surface against which theactuator engages and along which it is arranged to slide during acanister firing sequence.

The dose counter may include a counter pawl, the counter pawl having atooth arranged to engage the incremental output member, the tooth andincremental output member being arranged to permit one way onlyincremental relative motion therebetween. When the incremental outputmember comprises a ratchet wheel, the tooth can therefore serve as ananti-back drive tooth for the ratchet wheel, thereby permitting only oneway motion or rotation thereof.

The counter pawl may be substantially fixedly mounted on the main bodyof the incremental count system and the counter pawl may be arranged tobe capable of repeatedly engaging equi-spaced teeth of the incrementaloutput member in anti-back drive interlock configurations as the counteris operated. The counter pawl may be positioned so that the incrementaloutput member is halfway, or substantially halfway moved from oneanti-back drive interlock configuration to the next when the actuatorand incremental output member are in the end configuration thereof. Thisis highly advantageous in that it minimises the risk of double countingor non-counting by the dose counter.

According to a further aspect of the invention there is provided aninhaler comprising a main body arranged to retain a medicament canisterof predetermined configuration and a dose counter mounted in the mainbody.

The inhaler main body may include a canister receiving portion and aseparate counter chamber, the dose counter being located within the mainbody thereof, the incremental output member and actuator thereof insidethe counter chamber, the main body of the inhaler having wall surfacesseparating the canister-receiving portion and the counter chamber, thewall surfaces being provided with a communication aperture, an actuationmember extending through the communication aperture to transmit canistermotion to the actuator.

According to a further aspect of the present invention there is aprovided an inhaler for metered dose inhalation, the inhaler comprisinga main body having a canister housing arranged to retain a medicamentcanister for motion therein, and a dose counter, the dose counter havingan actuation member having at least a portion thereof located in thecanister housing for operation by movement of a medicament canister,wherein the canister housing has an inner wall, and a first inner wallcanister support formation located directly adjacent the actuationmember.

This is highly advantageous in that the first inner wall canistersupport formation can prevent a canister from rocking too much relativeto the main body of the inhaler. Since the canister may operate theactuation member of the dose counter, this substantially improves dosecounting and avoids counter errors.

The canister housing may have a longitudinal axis which passes through acentral outlet port thereof, the central outlet port being arranged tomate with an outer canister fire stem of a medicament canister, theinner wall canister support formation, the actuation member and theoutlet port lying in a common plane coincident with the longitudinalaxis. Accordingly, this construction may prevent the canister fromrocking towards the position of the dose counter actuation member,thereby minimising errors in counting.

The canister housing may have a further inner canister wall supportformation located on the inner wall opposite, or substantially opposite,the actuation member. Accordingly, the canister may be supported againstrocking motion away from the actuator member so as to minimise counterrors.

The canister housing may be generally straight and tubular and may havean arrangement in which each said inner wall support formation comprisesa rail extending longitudinally along the inner wall.

Each said rail may be stepped, in that it may have a first portionlocated towards a medicine outlet end or stem block of the canisterhousing which extends inwardly a first distance from a main surface ofthe inner wall and a second portion located toward an opposite end ofthe canister chamber which extends inwardly a second, smaller distancefrom the main surface of the inner wall. This may therefore enable easyinsertion of a canister into the canister housing such that a canistercan be lined up gradually in step wise function as it is inserted intothe canister housing.

The inhaler may include additional canister support rails which arespaced around an inner periphery of the inner wall of the canisterhousing and which extend longitudinally therealong.

At least one of the additional rails may extend a constant distanceinwardly from the main surface of the inner wall.

At least one of the additional rails may be formed with a similarconfiguration to the first inner wall canister support formation.

The dose counter may, apart from said at least a portion of theactuation member, be located in a counter chamber separate from thecanister housing, the actuation member comprising a pin extendingthrough an aperture in a wall which separates the counter chamber andthe canister housing.

According to a further aspect of the present invention there is providedan inhaler for inhaling medicaments having: a body for retaining amedicament store; the body including a dose counter, the dose counterhaving a moveable actuator and a return spring for the actuator, thereturn spring having a generally cylindrical and annular end; the bodyhaving a support formation therein for supporting said end of the returnspring, the support formation comprising a shelf onto which said end isengageable and a recess below the shelf.

This shelf and recess arrangement is highly advantageous since it allowsa tool (such as manual or mechanical tweezers) to be used to place thereturn spring of the actuator onto the shelf with the tool then beingwithdrawn at least partially via the recess.

The shelf may be U-shaped.

The support formation may include a U-shaped upstanding wall extendingaround the U-shaped shelf, the shelf and upstanding wall thereby forminga step and riser of a stepped arrangement.

The recess below the shelf my also be U-shaped.

At least one chamfered surface may be provided at an entrance to theshelf. This may assist in inserting the actuator and return spring intoposition.

A further aspect of the invention provides a method of assembly of aninhaler which includes the step of locating said end of said spring onthe shelf with an assembly tool and then withdrawing the assembly toolat least partly via the recess. This assembly method is highlyadvantageous compared to prior art methods in which spring insertion hasbeen difficult and in which withdrawal of the tool has sometimesaccidentally withdrawn the spring again.

The cylindrical and annular end of the spring may be movable in adirection transverse to its cylindrical extent into the shelf whilebeing located thereon.

According to a further aspect of the present invention there is providedan inhaler for inhaling medicament, the inhaler having a body forretaining a medicament store; and a dose counter, the dose counterhaving a moveable actuator and a chassis mounted on the body; thechassis being heat staked in position on the body. This is be highlyadvantageous in that the chassis can be very accurately positioned andheld firmly in place, thereby further improving counting accuracycompared to prior art arrangements in which some movement of the chassisrelative to the body may be tolerated in snap-fit connections.

The chassis may have at least one of a pin or aperture heat staked to arespective aperture or pin of the body.

The chassis may have a ratchet counter output member mounted thereon.

The ratchet counter output member may comprise a ratchet wheel arrangedto reel in incrementally a dose meter tape having a dosage indicialocated thereon.

According to a further aspect of the present invention there is provideda method of assembling an inhaler including the step of heat staking thechassis onto the body. The step of heat staking is highly advantageousin fixedly positioning the chassis onto the body in order to achievehighly accurate dose counting in the assembled inhaler.

The method of assembly may include mounting a spring-returned ratchetactuator in the body before heat staking the chassis in place. Themethod of assembly may include pre-assembling the chassis with a dosemeter tape prior to the step of heat staking the chassis in place. Themethod of assembly may include attaching a dose meter cover onto thebody after the heat staking step. The cover may be welded onto the bodyor may in some embodiments be glued or otherwise attached in place.

According to a further aspect of the present invention there is providedan inhaler for inhaling medicament and having a body, the body have amain part thereof for retaining a medicament store; and a dose counter,the dose counter being located in a dose counter chamber of the bodywhich is separated from the main part of the body, the dose counterchamber of the body having a dosage display and being perforated so asto permit the evaporation of water or aqueous matter in the dose counterchamber into the atmosphere.

This is high advantageous since it enables the inhaler to be thoroughlywashed and the dose counting chamber can thereafter dry out fully.

The display may comprise a mechanical counter display inside the dosecounter chamber and a window for viewing the mechanical counter display.The mechanical counter display may comprise a tape. The perforated dosecounter chamber may therefore enable reliable washing of the inhaler, ifdesired by the user, and may therefore dry out without the displaywindow misting up.

The dose counter chamber may be perforated by a drain hole formedthrough an outer hole of the body. The drain hole may be located at abottom portion of the body of the inhaler, thereby enabling fulldraining of the inhaler to be encouraged after washing when the inhaleris brought into an upright position.

According to a further aspect of the present invention there is provideda dose counter for an inhaler, the dose counter having a display tapearranged to be incrementally driven from a tape stock bobbin onto anincremental tape take-up drive shaft, the bobbin having an internal boresupported by and for rotation about a support shaft, at least one of thebore and support shaft having a protrusion which is resiliently biasedinto frictional engagement with the other of the bore and support shaftwith longitudinally extending mutual frictional interaction. Thisarrangement may provide good friction for the bobbin, thereby improvingtape counter display accuracy and preventing the bobbin from unwindingundesirably for example if the inhaler is accidentally dropped.

The support shaft may be forked and resilient for resiliently biasingthe support shaft and bore into frictional engagement.

The support shaft may have two forks, or more in some cases, each havinga radially extending protrusion having a friction edge extendingtherealong parallel to a longitudinal axis of the support shaft forfrictionally engaging the bore of the support shaft with longitudinallyextending frictional interaction therebetween.

The bore may be a smooth circularly cylindrical or substantiallycylindrical bore.

Each of the above inhalers in accordance with aspects of the presentinvention may have a medicament canister mounted thereto.

The canister may comprise a pressurised metered dose canister having areciprocally movable stem extending therefrom and movable into a maincanister portion thereof for releasing a metered dose of medicamentunder pressure, for example by operating a metered dose valve inside thecanister body. The canister may be operable by pressing by hand on themain canister body.

In cases in which one or more support rails or inner wall supportformations are provided, the canister may at all times when within thecanister chamber have a clearance of about 0.25 to 0.35 mm from thefirst inner wall support formation. The clearance may be almost exactly0.3 mm. This clearance which may apply to the canister body itself or tothe canister once a label has been applied, is enough to allow smoothmotion of the canister in the inhaler while at the same time preventingsubstantial rocking of the canister which could result in inaccuratecounting by a dose counter of the inhaler, especially when lower face ofthe canister is arranged to engage an actuator member of the dosecounter for counting purposes.

According to a further aspect of the invention, a method of assembling adose counter for an inhaler comprises the steps of providing a tape withdosing indicia thereon; providing tape positioning indicia on the tape;and stowing the tape while monitoring for the tape positioning indiciawith a sensor. The method advantageously permits efficient and accuratestowing of the tape, e.g. by winding.

The dosing indicia may be provided as numbers, the tape positioningindicia may be provided as one or more lines across the tape. Thestowing step comprises winding the tape onto a bobbin or shaft, and,optionally, stopping winding when the positioning indicia are in apredetermined position. The tape may be provided with pixelated indiciaat a position spaced along the tape from the positioning indicia. Thetape may also be provided with a priming dot.

According to a further aspect of the invention, a tape system for a dosecounter for an inhaler has a main elongate tape structure, and dosingindicia and tape positioning indicia located on the tape structure. Thetape positioning indicia may comprise at least one line extending acrossthe tape structure. The tape system may comprise pixelated indicialocated on the tape structure and spaced from the positioning indicia.The tape system may comprise a priming dot located on the tapestructure. The positioning indicia may be located between the timing dotand the pixelated indicia. The main elongate tape structure may have atleast one end thereof wound on a bobbin or shaft.

A further aspect of the invention provides a method of designing anincremental dose counter for an inhaler comprising the steps ofcalculating nominal canister fire and dose counter positions for a dosecounter actuator of the inhaler; calculating a failure/success rate fordose counters built to tolerance levels for counting each fire ofinhalers in which the dose counter actuators may be applied; andselecting a tolerance level to result in said failure/success rate to beat or below/above a predetermined value. This is highly advantageous inthat it allows an efficient and accurate prediction of the reliabilityof a series of inhaler counters made in accordance with the design.

The method of designing may include selecting the failure/success rateas a failure rate of no more than one in 50 million. The method ofdesigning may include setting an average count position for dosecounters built to the tolerances to be at or after an average fireposition thereof during canister firing motion. The method of designingmay include setting the average count position to be about 0.4 to 0.6 mmafter the average fire position, such as about 0.48 mm after. The methodof designing may include setting tolerances for the standard deviationof the fire position in dose counters built to the tolerances to beabout 0.12 to 0.16 mm, such as about 0.141 mm. The method of designingmay include setting tolerances for the standard deviation of the countpositions in dose counters built to the tolerances to be about 0.07 to0.09 mm, such as about 0.08 mm. A further aspect of the inventionprovides a computer implemented method of designing an incremental dosecounter for an inhaler which includes the aforementioned method ofdesigning.

A further aspect of the invention provides a method of manufacturing ina production run a series of incremental dose counters for inhalerswhich comprises manufacturing the series of dose counters in accordancewith the aforementioned method of designing.

A further aspect of the invention provides a method of manufacturing aseries of incremental dose counters for inhalers, which comprisesmanufacturing the dose counters with nominal canister fire and dosecount positions of a dose counter actuator relative to a dose counterchassis (or inhaler main body), and which includes building the dosecounters with the average dose count position in the series being, incanister fire process, at or after the average canister fire position inthe series.

According to a further aspect of the invention, the method providesfitting each dose counter in the series of incremental dose counters toa corresponding main body of an inhaler.

These aspects advantageously provide for the production run of a seriesof inhalers and dose counters which count reliably in operation.

According to a further aspect of the invention, an incremental dosecounter for a metered dose inhaler has a body arranged to retain acanister for movement of the canister relative thereto, the incrementaldose counter having a main body, an actuator arranged to be driven andto drive an incremental output member in a count direction in responseto canister motion, the actuator being configured to restrict motion ofthe output member in a direction opposite to the count direction. Thisadvantageously enables an inhaler dose counter to keep a reliable countof remaining doses even if dropped or otherwise jolted.

The output member may comprise a ratchet wheel. The actuator maycomprise a pawl and in which the ratchet wheel and pawl are arranged topermit only one-way ratcheting motion of the wheel relative to the pawl.The dose counter may include an anti-back drive member fixed to the mainbody. In a rest position of the dose counter, the ratchet wheel iscapable of adopting a configuration in which a back surface of one tooththereof engages the anti-back drive member and the pawl is spaced froman adjacent back surface of another tooth of the ratchet wheel withoutpositive drive/blocking engagement between the pawl and wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be carried out in various ways and preferredembodiment of a dose counter, inhaler and methods of assembly, designand manufacture will now be described with reference to the accompanyingdrawings in which:

FIG. 1 is an isometric view of a main body of an embodiment of aninhaler related to the invention together with a mouthpiece captherefor;

FIG. 2 is a top plan view of the components as shown in FIG. 1;

FIG. 3A is a section on the plane 3A-3A in FIG. 2;

FIG. 3B is a view corresponding to FIG. 3A but with a dose counterfitted to the main body of the inhaler;

FIG. 4A is an exploded view of the inhaler main body, mouthpiece cap,dose counter and a dose counter window;

FIG. 4B is a view in the direction 4B in FIG. 4C of a spring retainer ofthe dose counter;

FIG. 4C is a top view of the spring retainer of FIG. 4B;

FIG. 5 is a bottom view of the assembled inhaler main body, mouthpiececap, dose counter and dose counter window;

FIGS. 6A, 6B, 6C, 6D, 6E, 6F, 6G and 6H are various views of dosecounter components of the inhaler;

FIGS. 7A and 7B are sectional views showing canister clearance insidethe main body of the inhaler;

FIG. 7C is a further sectional view similar to that of FIG. 7B but withthe canister removed;

FIG. 7D is a top plan view of the inhaler main body;

FIGS. 8A, 8B, 8C and 8D show the inhaler main body and dose countercomponents during assembly thereof;

FIG. 9 shows a sectional side view of a datum line for an actuator pawlof the dose counter;

FIGS. 10A, 10B, 10C, 10D, 10E and 10F show various side views ofpositions and configurations of the actuator pawl, a ratchet wheel, anda count pawl;

FIG. 11 shows distributions for tolerances of start, reset, fire, countand end positions for the actuator of the dose counter;

FIG. 12 is an enlarged version of part of FIG. 4A;

FIG. 13 shows an end portion of a tape of the dose counter;

FIG. 14 shows a computer system for designing the dose counter;

FIG. 15 is an isometric view of a stock bobbin modified in accordancewith the present invention for use in the dose counter of the inhaler ofFIGS. 1 to 14;

FIG. 16 shows an end view of the stock bobbin of FIG. 15;

FIG. 17 is a section through a longitudinal axis of the stock bobbin ofFIGS. 15 and 16;

FIGS. 18A to 18C are views of the stock bobbin of FIGS. 15 to 17 mountedin the dose counter chassis of FIGS. 1 to 14, with the control elementsof the forks of the second shaft (or split pin) having a profileslightly different to that in FIG. 6F, with the forks in a compressedconfiguration;

FIGS. 19A to 19C are views equivalent to FIGS. 18A to 18C but with theforks in a more expanded configuration due to a different rotationalposition of the stock bobbin;

FIG. 20 is an isometric view of the chassis assembled and including thestock bobbin of FIGS. 15 to 17 but excluding the tape for reasons ofclarity;

FIG. 21 is a view of a preferred embodiment of a dry powder inhaler inaccordance with the present invention;

FIG. 22 is an exploded view of the inhaler of FIG. 21;

FIG. 23 is a view of a dose counter of the inhaler of FIG. 21;

FIG. 24 is an exploded view of the dose counter shown in FIG. 23;

FIG. 25 is an exploded view of parts of the inhaler of FIG. 21; and

FIG. 26 is a view of a yoke of the inhaler of FIG. 21.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a main body 10 of a manually operated metered dose inhaler12 in accordance with an embodiment related to the present invention andhaving a mouthpiece cap 14 securable over a mouthpiece 16 of the mainbody.

The main body has a canister chamber 18 into which a canister 20 (FIG.7A) is slideable. The canister 20 has a generally cylindrical main sidewall 24, joined by a tapered section 26 to a head portion 28 having asubstantially flat lower face 30 which has an outer annular drivesurface 32 arranged to engage upon and drive an actuation pin 34 of adose counter 36 as will be described. Extending centrally and axiallyfrom the lower face 30 is a valve stem 38 which is arranged to sealinglyengage in a valve stem block 40 of the main body 10 of the inhaler 12.The valve stem block 40 has a passageway 42 leading to a nozzle 44 fordirecting the contents of the canister 20, namely active drug andpropellant, towards an air outlet 46 of the inhaler main body 12. Itwill be appreciated that due to gaps 48 between the canister 20 and aninner wall 50 of the main body 10 of the inhaler 12 an open top 52 ofthe main body 10 forms an air inlet into the inhaler 12 communicatingvia air passageway 54 with the air outlet 46, such that canistercontents exiting nozzle 44 mix with air being sucked by the user throughthe air passageway 54 in order to pass together through the air outletand into the mouth of the user (not shown).

The dose counter 36 will now be described. The dose counter 36 includesan actuation pin 34 biased upwardly from underneath by a return spring56 once installed in the main body 10. As best shown in FIGS. 4A, 6H and8A, the pin 34 has side surfaces 58, 60 arranged to slide betweencorresponding guide surfaces 62, 64 located in a dose counter chamber 66of the main body 10, as well as an end stop surface 68 arranged toengage a corresponding end stop 70 formed in the dose counter chamber 66to limit upward movement of the pin 34. The pin 34 has a top part 72which is circularly cylindrical and extends through an aperture 74formed through a separator wall 76 which separates the canister chamber18 from the dose counter chamber 66. The top part 72 of the pin 34 has aflat top surface 78 which is arranged to engage the outer annular drivesurface 32 of the canister 20.

The actuation pin 34 is integrally formed with a drive or actuator pawl80. The actuator pawl 80 has a generally inverted U-shape configuration,having two mutually spaced and parallel arms 82, 84 extending from abase portion of the actuation pin 34, each holding at respective distalends 88 thereof opposite ends of a pawl tooth member 90 which extends ina direction substantially perpendicular to the arms 82, 84, so as toprovide what may be considered a “saddle” drive for pulling on each ofthe 11 drive teeth 92 of a ratchet wheel 94 of an incremental drivesystem 96 or ratchet mechanism 96 of the dose counter 36. As shown forexample in FIG. 10B, the pawl tooth member 90 has a sharp lowerlongitudinal side edge 98 arranged to engage the drive teeth 92, theedge-to-surface contact provided by this engagement providing veryaccurate positioning of the actuator pawl 80 and resultant rotationalpositioning of the ratchet wheel 94.

The dose counter 36 also has a chassis preassembly 100 which, as shownin FIGS. 4A and 6A, includes a chassis 102 having a first shaft 104receiving the ratchet wheel 94 which is secured to a tape reel shaft106, and a second shaft (or split pin) 108 which is parallel to andspaced from the first shaft 104 and which slidably and rotationallyreceives a tape stock bobbin 110.

As shown in FIG. 6B, when the inhaler has not been used at all, themajority of a tape 112 is wound on the tape stock bobbin 110 and thetape 112 has a series of regularly spaced numbers 114 displayedtherealong to indicate a number of remaining doses in the canister 20.As the inhaler is repeatedly used, the ratchet wheel 94 is rotated bythe actuator pawl 80 due to operation of the actuation pin 34 by thecanister 20 and the tape 112 is incrementally and gradually wound on tothe tape reel shaft 106 from the second shaft 108. The tape 112 passesaround a tape guide 116 of the chassis 102 enabling the numbers 114 tobe displayed via a window 118 in a dose counter chamber cover 120 havinga dose marker 132 formed or otherwise located thereon.

As shown in FIGS. 6A and 6D, the second shaft 108 is forked with twoforks 124, 126. The forks 124, 126 are biased away from one another. Theforks have located thereon at diametrically opposed positions on thesecond shaft 108 friction or control elements 128, 130, one on eachfork. Each control element extends longitudinally along its respectivefork 124, 126 and has a longitudinally extending friction surface 132,134 which extends substantially parallel to a longitudinal axis of thesecond shaft and is adapted to engage inside a substantially cylindricalbore 136 inside the tape stock bobbin 110. This control arrangementprovided between the bore 136 and the control elements 128, 130 providesgood rotational control for the tape stock bobbin 110 such that it doesnot unwind undesirably such as when the inhaler is dropped. The tapeforce required to unwind the tape stock bobbin 110 and overcome thisfriction force is approximately 0.1 N.

As can be seen in FIG. 6D, as well as FIGS. 6G and 10A to 10F, thechassis 102 is provided with an anti-back drive tooth 138 or count pawl138 which is resiliently and substantially fixedly mounted thereto. Aswill be described below and as can be seen in FIGS. 10A to 10F, when theactuation pin 34 is depressed fully so as to fire the metered valve (notshown) inside the canister 20, the actuator pawl 80 pulls down on one ofthe teeth 92 of the ratchet wheel 94 and rotates the wheel 94anticlockwise as shown in FIG. 6D so as to jump one tooth 92 past thecount pawl 138, thereby winding the tape 112 a distance incrementallyrelative to the dose marker 122 on the dose counter chamber 120 so as toindicate that one dose has been used.

With reference to FIG. 10B, the teeth of the ratchet wheel 94 have tips143 which are radiused with a 0.1 mm radius between the flat surfaces140, 142. The ratchet wheel 94 has a central axis 145 which is 0.11 mmabove datum plane 220 (FIG. 9). A top/nose surface 147 of the anti-backdrive tooth 138 is located 0.36 mm above the datum plane 220. Thedistance vertically (i.e. transverse to datum plane 220—FIG. 9) betweenthe top nose surface 147 of the anti-back drive tooth is 0.25 mm fromthe central axis 145 of the wheel 94. Bump surface 144 has a lateralextent of 0.20 mm, with a vertical length of a flat 145′ thereof being 1mm, the width of the bump surface being 1.22 mm (in the direction of theaxis 145), the top 149 of the bump surface 144 being 3.02 mm verticallybelow the axis 145, and the flat 145′ being spaced a distance sideways(i.e. parallel to the datum plane 220) 2.48 mm from the axis 145. Thetop surface 78 of the pin 34 (FIG. 6H) is 11.20 mm above the datum plane220 (FIG. 9) when the actuator pawl 80 and pin 34 are in the startconfiguration. The length of the valve stem 22 is 11.39 mm and the drivesurface 32 of the canister 20 is 11.39 mm above the datum plane 220 whenthe canister is at rest waiting to be actuated, such that there is aclearance of 0.19 mm between the canister 20 and the pin 34 in thisconfiguration.

FIGS. 10A and 10B show the actuator pawl 80 and ratchet wheel 94 andcount pawl 138 in a start position in which the flat top 78 of the pin34 has not yet been engaged by the outer annular drive surface 32 of thecanister 20 or at least has not been pushed down during a canisterdepression.

In this “start” position, the count pawl 138 engages on a non-returnback surface 140 of one of the teeth 92 of the ratchet wheel 94. Thelower side edge 98 of the actuator pawl is a distance “D” (FIG. 9) 1.33mm above datum plane 220 which passes through bottom surface or shoulder41 of valve stem block 40, the datum plane 220 being perpendicular to amain axis “X” of the main body 10 of the inhaler 12 which is coaxialwith the centre of the valve stem block bore 43 and parallel to adirection of sliding of the canister 20 in the main body 10 of theinhaler 12 when the canister is fired.

As shown in FIG. 10B, an advantageous feature of the construction isthat the pawl tooth/actuator 90 acts as a supplementary anti-back drivemember when the inhaler 12 is not being used for inhalation. Inparticular, if the inhaler 12 is accidentally dropped, resulting in ajolt to the dose counter 36 then, if the wheel 94 would try to rotateclockwise (backwards) as shown in FIG. 10B, the back surface 140 of atooth will engage and be blocked by the tooth member 90 of the pawl 80.Therefore, even if the anti-back drive tooth 138 is temporarily bent orovercome by such a jolt, undesirable backwards rotation of the wheel 94is prevented and, upon the next canister firing sequence, the pawl 90will force the wheel 94 to catch up to its correct position so that thedose counter 36 continues to provide correct dosage indication.

FIG. 10C shows a configuration in which the actuator pawl 80 has beendepressed with the pin 34 by the canister 20 to a position in which theside edge 98 of the pawl tooth member 90 is just engaged with one of theteeth 92 and will therefore upon any further depression of the pin 34begin to rotate the wheel 94. This is referred to as a “Reset” positionor configuration. In this configuration, the lower side edge 98 of theactuator 80 is 0.64 mm above the datum plane 220.

FIG. 10D shows a configuration in which the actuator pawl 80 has beenmoved to a position lower than that shown in FIG. 10C and in which themetered dose valve (not shown) inside the canister has at this veryposition fired in order to eject active drug and propellant through thenozzle 44. It will be noted that in this configuration the count pawl138 is very slightly spaced from the back surface 140 of the same tooth92 that it was engaging in the configuration of FIG. 10D. Theconfiguration shown in FIG. 10D is known as a “Fire” configuration. Inthis configuration the lower side edge 98 of the actuator 80 is 0.47 mmbelow the datum plane 220.

FIG. 10E shows a further step in the sequence, called a “Count” positionin which the actuator pawl 80 has rotated the ratchet wheel 94 by thedistance circumferentially angularly between two of the teeth 92, suchthat the count pawl 138 has just finished riding along a forward surface142 of one of the teeth 92 and has resiliently jumped over the toothinto engagement with the back surface 140 of the next tooth.Accordingly, in this “Count” configuration, a sufficiently long strokemovement of the pin 34 has occurred that the tape 112 of the dosecounter 36 will just have counted down one dose. In this configuration,the lower side edge 98 of the actuator is 0.95 mm below the datum plane220. Accordingly, in this position, the actuator 80 generally, includingedge 98, is 0.48 mm lower than in the fire configuration. It has beenfound that, although the count configuration happens further on than thefire configuration, counting is highly reliable, with less than one in50 failed counts per million. This is at least partially due to momentumeffects and to the canister releasing some back pressure on the user insome embodiments as its internal metering valve fires.

In the configuration of FIG. 10F, the pawl 80 has been further depressedwith the pin 34 by the canister 20 to a position in which it is justdisengaging from one of the teeth 92 and the actuator pawl 80 isassisted in this disengagement by engagement of one of the arms 84 witha bump surface 144 on the chassis 102 (see FIG. 6G) and it will be seenat this point of disengagement, which is called an “End” configuration,the count pawl 138 is positioned exactly halfway or substantiallyhalfway between two of the drive teeth 92. This advantageously meanstherefore that there is a minimum chance of any double counting ornon-counting, which would be undesirable. In the end configuration, theside edge 98 of the actuator is 1.65 mm below the datum plane 220. Itwill be appreciated that any further depression of the actuator pawl 80and pin 34 past the “End” configuration shown in FIG. 10F will have noeffect on the position of the tape 112 displayed by the dose counter 36since the actuator pawl 80 is disengaged from the ratchet wheel 94 whenit is below the position shown in FIG. 10F.

As shown in FIGS. 7C and 7D, the inner wall 50 of the main body 10 isprovided with a two-step support rail 144 which extends longitudinallyalong inside the main body and is located directly adjacent the aperture74. As shown in FIG. 7B a diametrically opposed two-step support rail146 is also provided and this diametrically opposed in the sense that avertical plane (not shown) can pass substantially directly through thefirst rail 144, the aperture 74, a central aperture 148 of the valvestem block 40 (in which canister stem 25 is located) and the secondtwo-step support rail 146. As shown in FIG. 7A and schematically in FIG.7B, the rails 144, 146 provide a maximum clearance between the canister20 and the rails 144, 146 in a radial direction of almost exactly 0.3mm, about 0.25 to 0.35 mm being a typical range. This clearance in thisplane means that the canister 20 can only rock backwards and forwards inthis plane towards away from the actuation pin 34. A relatively smalldistance and this therefore prevents the canister wobbling and changingthe height of the actuation pin 34 a as to undesirably alter theaccuracy of the dose counter 36. This is therefore highly advantageous.

The inner wall 50 of the main body 10 is provided with two furthertwo-step rails 150 as well as two pairs 152, 154 of rails extendingdifferent constant radial amounts inwardly from the inner wall 50, so asto generally achieve a maximum clearance of almost exactly 0.3 mm aroundthe canister 20 for all of the rails 144, 146, 150, 152, 154 spacedaround the periphery of the inner wall 50, in order to prevent unduerocking while still allowing canister motion freely inside the inhaler12. It will be clear from FIG. 7C for example that the two-step railshave a first portion near an outlet end 156 of the canister chamber 18,the first portion having a substantially constant radial orinwardly-extending width, a first step 160 leading to a second portion162 of the rail, the second portion 102 having a lesser radial orinwardly extending extent than the first portion 156, and finally asecond step 164 at which the rail merges into the main inner wall 50main surface.

A method of assembling the inhaler 12 will now be described.

With reference to FIG. 8A, the main body 10 of the inhaler 12 is formedby two or more plastics mouldings which have been joined together to theconfiguration shown.

As shown in FIG. 8B, the actuator pawl 80 and pin 34 are translatedforward into position into a pin receiving area 166 in the dose counterchamber 66 and the pin 34 and actuator 80 may then be raised until thepin 34 emerges through the aperture 74.

Next, the return spring 56 may be inserted below the pin 34 and agenerally cylindrical annular lower end 168 of the spring 56 may bemoved by a tweezer or tweezer-like assembly tool (not shown) intoengagement with a shelf 170 of a spring retainer 172 in the dose counterchamber 66. The spring retainer 172 is U-shaped and the shelf 170 isU-shaped and has a recess 174 formed below it. As shown in FIGS. 4B, 4Cand 12 shelf 170 includes three chamfer surfaces 176, 178, 180 arrangedto assist in moving the lower end of the spring 168 into position ontothe shelf using the assembly tool (not shown). Once the lower end of thespring 168 is in place, the assembly tool (not shown) can easily beremoved at least partly via the recess 174 below the lower end 168 ofthe spring 56.

The tape 112 is attached at one end (not shown) to the tape stock bobbin110 and is wound onto the bobbin by a motor 200 (FIG. 13) having ahexagonal output shaft 202 which engages in a hexagonal socket 204 (FIG.6B) of the bobbin. During winding, the tape is monitored by a sensor206, which may be in the form of a camera or laser scanner, which feedsdata to a computer controller 205 for the motor 200. The controller 205recognises three positioning markers 210 in the form of lines across thetape 112 and stops the motor 202 when the tape 112 is nearly fully woundonto the bobbin 110, such that the distal end 212 of the tape 112 can besecured, e.g. by adhesive, to the tape reel shaft 106. The controller205 also recognises a pixelated tape size marker 214 observed by thesensor 206 and logs in a stocking system data store 217 details of thetape 112 such as the number of numbers 114 on the tape, such as onehundred and twenty or two hundred numbers 114. Next, the tape reel shaftis wound until an appropriate position of the lines 210 at which apriming dot 216 will, once the bobbin 110 and reel shaft 106 are slidonto the second shaft 108 and second shaft 104, be in a position to belocated in the window 118 when the inhaler 12 is fully assembled. In theembodiments, the bobbin 110 and reel shaft 106 may be slid onto theshafts 108, 104 before the tape 112 is secured to the reel shaft 106 andthe reel shaft may then be wound to position the priming dot 216.

Next, the assembled dose counter components of the chassis preassembly100 shown in FIG. 6B may as shown in FIG. 8C be inserted into the dosecounter chamber 66, with pins 182, 184, 186 formed on the main body 10in the dose counter chamber 66 passing through apertures or slots 188,190, 192 formed on the chassis 102, such that the pins 182, 184, 186extend through (or at least into) the apertures or slots 188, 190, 192.With the chassis 102 being relatively firmly pushed towards the mainbody 10, the pins 182, 184, 186 are then heat staked and the chassis 102is therefore after this held very firmly in position in the main bodyand is unable to move, thereby assisting in providing great accuracy forthe dose counter 36. Next, as shown in FIG. 8D, the dose counter chambercover 120 may be fitted over the dose counter chamber 66 and may besecured in place such as by welding, with the priming dot 216 beingdisplayed through the window.

The user can, when readying the inhaler 12 for first use, prime theinhaler by depressing the canister 20 three times which will bring thefirst number 114 on the tape into display through the window 118 inplace of the priming dot 216, the number 114 shown in FIG. 8D being“200”, thereby indicating that 200 doses are remaining to be dispensedfrom the canister 20 and inhaler 12.

As shown in FIG. 8D, and in FIG. 5, an open drain hole 194 is providedat the bottom of the dose counter chamber 66 by a substantiallysemi-circular cut-out or recess formation 196 in a lower surface 198 ofthe main body 10 of the inhaler. Accordingly, if the user (not shown)should decide to wash the main body 10 of the inhaler, for example afterencountering an unhygienic situation or simply as a matter of choice,the drain hole 194 allows initial draining of water from inside the dosecounter chamber 66 and also thereafter evaporation of water or anyaqueous matter in the dose counter chamber 66 so that the window 118does not mist up undesirably.

FIG. 14 shows a computer system 230 for designing the dose counter 36and in particular for calculating distributions representative ofaverage positions and standard deviations in a production series ofinhalers of the start, reset, fire, count and end positions of theactuator lower side edge 98 relative to the datum plane 220 (FIG. 9) andtherefore of the actuator pawl 80 generally relative to the ratchetwheel 94, chassis 102 and, when the inhaler 12 is fully assembled, themain body 10 of the inhaler 12. The computer system 230 includes a datastore 232, a CPU 234, an input device 236 (such as a keyboard orcommunication port) and an output device 238 (such as a communicationsport, display screen and/or printer). A user may enter data via theinput device 236 which may be used by the CPU 234 in a mathematicalcalculation to predict count failure rates when the various dosecounters are to be built in a series with dose counter positions setwith given averages and standard deviations and taking into account anymomentum/inertia effects and metering valve user-back-pressure reductioneffect which will occur upon canister firing of a given type ofcanister. The computer system 230 is thus mathematically used to designthe distributions. For the inhaler 12 described herein with the dosecounter 36 and canister 20, the distributions are designed as shown inFIG. 11. The x axis shows distance of the lower side surface 98 of theactuator 80 above the datum plane 220 and the y axis is representativeof the distribution. Thus, curve 240 shows that the start configurationhas an average 1.33 mm above the datum plane 200 (standard deviation is0.1 mm), curve 242 shows that the reset configuration has an average of0.64 mm above the datum plane 220 (standard deviation is 0.082 mm),curve 244 shows the fire configuration has an average 0.47 mm below thedatum plane 220 (standard deviation is 0.141 mm), curve 246 shows thecount configuration has an average 0.95 mm below the datum plane 220(standard deviation is 0.080 mm), and curve 248 shows the endconfiguration has an average of 1.65 mm below the datum plane 220(standard deviation is 0.144 mm).

FIGS. 15 to 20 show a version of the inhaler modified in accordance withthe present invention. In these drawings, the same reference numeralshave been used to those in the earlier drawings to denote the equivalentcomponents. The inhaler 12 is the same as that in FIGS. 1 to 14 apartfrom the following modifications.

First, it can be seen that there is a modification in that the driveteeth 92 of the ratchet wheel 94 have a different profile to that inFIGS. 1 to 14. There are also only nine ratchet teeth 94 in thisembodiment instead of eleven.

Additionally, as shown in FIGS. 18C and 19C, the control elements 128,130 on the forks 124, 126 of the second shaft 108 have a tapered profilewhich is different to the profile of the control elements 128, 130 shownin FIG. 6F. Either profile can be used in the embodiment of FIGS. 15 to20 however.

Furthermore, as shown in FIG. 15, the tape stock bobbin 110 has aninwardly facing generally cylindrical engagement surface 300 with awavelike form extending partially therealong. The engagement surface 300has a cross-section 301 perpendicular to the longitudinal length of thestock bobbin 110 which is constant therealong. This cross-section 301can be seen in FIG. 16 and consists of a series of ten regularly spacedconcavities 302 and ten convex wall portions 304. The convex wallportions 304 are equi-spaced between the concavities 302. Each concavity302 has a radius of 0.2 mm. Each convex wall portion 304 also has aradius of 0.2 mm. Finally, the cross section 301 also includes flat wallportions 306 between all of the radiused wall portions of theconcavities 302 and convex wall portions 304. The geometry of thecross-section 301 is therefore defined by the radii of the concavities302 and convex wall portions 304, the flat wall portions 306 and thefact that there are ten concavities 302 and convex wall portions 304.

The minor diameter of the engagement surface 300, i.e. between the tipsof opposite convex wall portions 304, is 2.46 mm. The major diameter ofthe engagement surface 300, i.e. between the outermost portions of theconcavities 302, is 2.70 mm. The undeformed tip to tip maximum diameterof the forks 124, 126 of the split pin (the second shaft) 108, i.e. inthe region of the maximum radio extent of the control elements 128, 130,is 3.1 millimetres and it will therefore be appreciated that the forks124, 126 are resiliently compressed once the stock bobbin 110 has beenassembled onto the split pin 108 in all rotational configurations of thestock bobbin 110 relative to the split pin 108. The minimum gap betweenthe forks 124, 126 in the plane of the cross sections of FIGS. 18C and19C is 1 mm when the split pin 108 is in the undeformed, pre-insertedstate. When the split pin 108 is at maximum compression, as shown inFIGS. 18A to 18C when the control elements 128, 130 are shown to beengaged on top of the convex wall portions 304, the gap 308 between thetips 310, 312 of the forks 124, 126 is 0.36 mm. On the other hand, whenthe split pin 108 is at minimum compression (once inserted into thestock bobbin) as shown in FIGS. 19A to 19C, when the control elements128, 130 rest in the concavities 302, the gap between the tips 310, 312of the forks 124, 126 is 0.6 mm. The control elements 128, 130 areoutwardly radiused with a radius also of 0.2 mm such that they can justrest on the concavities 302 with full surface contact (at least at anaxial location on the split pin where the tapered control elements areat their maximum radial extent), without rattling in, locking onto orfailing to fit in the concavities 302. The radii of the control elements128, 130 is therefore preferably substantially the same as the radii ofthe concavities 302

It will be appreciated that whereas FIGS. 18B and 19B are end viewsalong the coaxial axis of the stock bobbin 110 and split pin 108, FIGS.18A and 19A are cross-sections. FIG. 19A is a section on the plane A-A′in FIG. 19C and FIG. 18A is a section at the same plane, but of coursewith the stock bobbin 110 rotated relative to the split pin 108.

As the inhaler 12 is used and the ratchet wheel 94 rotates in order tocount used doses, the stock bobbin rotates incrementally throughrotational positions in which rotation is resisted, i.e. due toincreasing compression of the split pin 108 at such rotationalpositions, and rotational positions in which rotation is promoted, i.e.due to decreasing compression of the split pin 108 at such rotationalpositions and this may involve a click forward of the stock bobbin 110to the next position equivalent to that in FIGS. 19A to 19C in which thecontrol elements 128, 130 of the split pin art located in theconcavities 302. This functionality firstly allows the stock bobbin tounwind during use as required, but also prevents the tape 112 fromloosening during transit if the inhaler 12 is dropped, such as onto ahard surface. This is highly advantageous, since the tape 11 isprevented from moving to a position in which it will give an incorrectreading regarding the number of doses in the canister.

During compression and expansion of the forks in the radial directionbetween the two configurations shown in FIGS. 18C and 19C, the forks124, 126 rotate about a point 316 on the split pin where the forks 124,126 come together. This rotational action means that there is a cammingaction between the forks 124, 126 and the engagement surface 300 withoutsignificant friction but, nevertheless, the resilient forces provided bythe regulator formed by the engagement surface 300 and forks 124, 126are able to regulate unwinding of the tape such that it does not easilyoccur during transit or if the inhaler 12 is dropped. It has been foundduring testing that a force of 0.3 to 0.4 N needs to be applied to thetape 112 to overcome the regulator at the stock bobbin 110. 0.32 N isachieved with the control elements 128 having the profile shown in FIG.19C and 0.38 N is achieved with the profile of the control elements 128altered to be as shown as described with reference to FIG. 6F. Theseforces are substantially higher than the 0.1 N force mentioned above andundesirable movement of the tape is substantially avoided even if theinhaler is dropped onto a hard surface. The modified arrangement ofFIGS. 15 to 20 does not provide this force “constantly” such that thereis overall not an undesirably high friction of the tape 112 as it passesover the other components of the dose counter because, due to theincremental nature of the resilient forces at the regulator, the tape112 can incrementally relax as it slides over the stationary chassiscomponents.

Instead of having ten concavities 302 and convex wall portions 304,other numbers may be used, such as 8 or 12. However, it is preferred tohave an even number, especially since two control elements 128, 130 areprovided, so that all of the control elements 128, 130 will expand andcontract simultaneously. However, other arrangements are envisaged with3 or more forks and the number of concavities/convex wall portions maybe maintained as an integer divisible by the number of forks to maintaina system with simultaneous expansion/contraction. For example, the useof 9, 12 or 15 concavities/convex wall portions with 3 forks isenvisaged.

Instead of having the engagement surface 300 on the inside of the stockbobbin 110, it could be placed on the outside of the stock bobbin 110 soas to be engaged by flexible external legs/pawls or similar.

It will be noted that the regulator provided by the engagement surface300 and forks 124, 126 does not only allow rotation of the stock bobbinin one direction as is the case with the ratchet wheel 94. Rotation inboth directions is possible, i.e. forwards and backwards. This meansthat during assembly, the stock bobbin 110 can be wound backwards duringor after fitting the bobbin 100, shaft 106 and tape 112 onto thecarriage 102, if desired.

The stock bobbin 110 and the carriage 102 including the split pin 108are both moulded of polypropylene material.

It will be seen from FIG. 16 that the cross-sectional shape 301 is notsymmetrical within the hexagonal socket 204. This has enabled thehexagonal socket 204 to be maintained at a useful size while stillallowing the desired size and geometry of the cross section 301 to fitwithout interfering with the hexagonal shape of the hexagonal socket 204and also permits moulding to work during manufacture.

As shown in FIG. 17, the stock bobbin 110 has a series of fourcircumferential ribs 330 inside it and a spaced therealong. These holdthe stock bobbin 110 on the correct side of the mould tool duringmoulding.

FIGS. 21 and 22 show a preferred embodiment in accordance with theinvention of an inhaler 510 for dispensing a dry-powdered medicament inmetered doses for patient inhalation. The inhaler 510 is as disclosed inFIGS. 1 to 16 or EP-A-1330280, the contents of which are hereby fullyincorporated herein by reference, but with the stock bobbin 110 andsecond shaft 108 of the dose counter 516 modified so as to be as inFIGS. 15 to 20 hereof. Thus, the dry powder inhaler 510 generallyincludes a housing 518, and an assembly 512 received in the housing (seeFIG. 21). The housing 518 includes a case 520 having an open end 522 anda mouthpiece 524 (FIG. 25) for patient inhalation, a cap 526 secured toand closing the open end 522 of the case 520, and a cover 528 pivotallymounted to the case 520 for covering the mouthpiece 524. As shown inFIG. 22, the inhaler 510 also includes an actuation spring 569, firstyoke 566 with opening 572, bellows 540 with crown 574, a reservoir 514,second yoke 568 with hopper 542 and dose counter 516 mounted thereto,and case 520 has transparent window 5130 thereon for viewing dosecounter tape indicia 5128. The dose metering system also includes twocams 570 mounted on the mouthpiece cover 528 and movable with the cover528 between open and closed positions. The cams 570 each include anopening 580 for allowing outwardly extending hinges 582 of the case 520to pass therethrough and be received in first recesses 584 of the cover528. The cams 570 also include bosses 586 extending outwardly andreceived in second recesses 588 of the cover 528, such that the cover528 pivots about the hinges 582 and the cams 570 move with the cover 528about the hinges 582. As described in EP-A-1330280, cams 570 act uponcam followers 578 to move second yoke 568 up and down and therebyoperate dose counter by engagement of pawl 5138 on the second yoke 568with teeth 5136. Remaining components of the inhaler are provided as,and operate as described, in EP-A-1330280.

The dose counting system 516 therefore includes a ribbon or tape 5128(FIGS. 23 & 24), having successive numbers or other suitable indiciaprinted thereon, in alignment with a transparent window 5130 provided inthe housing 18 (see FIG. 22). The dose counting system 516 includes therotatable stock bobbin 110 (as described above), an indexing spool 5134rotatable in a single direction, and the ribbon 5128 rolled and receivedon the bobbin 110 and having a first end 5127 secured to the spool 5134,wherein the ribbon 5128 unrolls from the bobbin 110 so that the indiciaare successively displayed as the spool 5134 is rotated or advanced. InFIGS. 23 and 24 the wavelike engagement surface 300 of the bobbin 110 isnot shown for the purposes of clarity.

The spool 134 is arranged to rotate upon movement of the yokes 566, 568to effect delivery of a dose of medicament from reservoir 514, such thatthe number on the ribbon 5128 is advanced to indicate that another dosehas been dispensed by the inhaler 510. The ribbon 5128 can be arrangedsuch that the numbers, or other suitable indicia, increase or decreaseupon rotation of the spool 5134. For example, the ribbon 5128 can bearranged such that the numbers, or other suitable indicia, decrease uponrotation of the spool 5134 to indicate the number of doses remaining inthe inhaler 510. Alternatively, the ribbon 5128 can be arranged suchthat the numbers, or other suitable indicia, increase upon rotation ofthe spool 5134 to indicate the number of doses dispensed by the inhaler10.

The indexing spool 5134 includes radially extending teeth 5136, whichare engaged by pawl 5138 extending from a cam follower 578 of the secondyoke 568 upon movement of the yoke to rotate, or advance, the indexingspool 5134. More particularly, the pawl 5138 is shaped and arranged suchthat it engages the teeth 5136 and advances the indexing spool 5134 onlyupon the mouthpiece cover 528 being closed and the yokes 566, 568 movedback towards the cap 526 of the housing 518.

The dose counting system 516 also includes a chassis 5140 that securesthe dose counting system to the hopper 542 and includes shafts 108, 5144for receiving the bobbin 110 and the indexing spool 5134. As describedabove with reference to FIGS. 1 to 20, the bobbin shaft 108 is forkedand includes radially nubs 5146 for creating a resilient resistance torotation of the bobbin 110 on the shaft 108 by engaging with thewavelike engagement surface 300 inside the bobbin 110. A clutch spring5148 is received on the end of the indexing spool 5134 and locked to thechassis 5140 to allow rotation of the spool 5134 in only a singledirection.

Various modifications may be made to the embodiment shown withoutdeparting from the scope of the invention as defined by the accompanyingclaims as interpreted under patent law.

What is claimed:
 1. An inhaler for inhaling medicament and having abody, the body have a main part thereof for retaining a medicamentstore; and a dose counter, the dose counter being located in a dosecounter chamber of the body which is separated from the main part of thebody, the dose counter chamber of the body having a dosage display and aperforation so as to permit the evaporation of water or aqueous matterin the dose counter chamber into the atmosphere.
 2. The inhaler asclaimed in claim 1, wherein the perforation is positioned at a bottomend of the dose counter chamber.
 3. The inhaler as claimed in claim 1,further comprising a cover that is fixed to the body to conceal the dosecounter chamber, and wherein the cover does not conceal the perforation.